豆乳凝固酶产生菌LD30的研究

Studies on soymilk-clotting enzyme producing bacteria LD30

目的从土壤中分离产豆乳凝固酶菌株，并研究其发酵条件和酶学性质。方法采用常规土壤分离方法和培养基。结果从广东、敦煌、吐鲁番等地得到的12份土壤样品中分离得到1株产豆乳凝固酶的菌株芽孢杆菌LD30。在给定的发酵条件下，豆乳凝固酶的产率达到600U·L^-1。酶学性质表明：该酶的最适反应温度为70℃，60℃保温1h，残余酶活力为50％。在pH6．0～7．0内，酶活力稳定，最适酶反应的pH值为5．9。结论筛选到的产豆乳凝固酶菌株芽孢杆菌LD30具有较高的产酶活性，值得进一步深入研究。

Objective To isolate strains producing soymilk-clotting enzyme and study its fermentation conditions and enzyme properties. Methods Regular soil isolation method and media were adopted. Results A strain Bacillus sp. LD30 producing soymilk-clotting enzyme was isolated from 12 soil samples obtained from Guangdong, Dunhuang, Tulufan, etc. Under given fermentation condition, the yield of soymilk-clotting enzyme was 600 U·L^-1. Investigation of enzymetic properties showed that the optimum enzymetic reaction temperature was 70℃, and 50 % of enzymetic activity was remained after 1 h incubation at 60℃. This enzyme was stable in the range of pH 6 - 7, and its optimum enzymetic reaction pH was 5.9. Conclusions The obtained strain Bacillus sp. LD30, having a relatively high soymilk-clotting producing ability, is worthy to study further.